1. Field of Invention
The field of the currently claimed embodiments of this invention relates to illumination systems, and more particularly to high-efficiency illumination systems.
2. Discussion of Related Art
Conventional illumination systems that illuminate through a waveguide or light pipe, such as endoscopic illumination systems, use bulky, high-intensity white light sources, such a xenon light sources. Xenon sources are inefficient in producing white light and conventional endoscopic illumination systems are inefficient in coupling the light that is produced into the light pipe. Such illumination systems are thus very bulky, inefficient and require relatively large power sources.
Light emitting diodes (LEDs) are compact and efficient light sources. However, LEDs are Lambertian light sources. The light emitted from the LED surface is non-directive and incoherent. Coupling such light with high efficiency into an endoscopic fiber optic light pipe is difficult, especially for a small gauge light pipe where the coupling efficiency is usually no more than a few percent.
Current commercial products, such as the CARCLO FIBER coupling lens, uses a parabolic-shape based design to collimate LED light into a large fiber optical cable with the diameter ranging from 8 to 12 mm; the average efficiency is 85%. Fraen Fiber Light Injector (FFLI) for LUXEON™ LEDs uses a similar design to couple light into 7-9 mm diameter fiber bundle or light pipe. The efficiency is 82% at the highest. However, there is a lack of highly efficient illumination systems that have smaller diameter light pipes, such as about 1 mm and smaller.
Therefore, there remains a need for improved illumination systems and optical couplers for efficient and compact illumination systems.